Advances in the processing of so-called “packets” of information have led to the introduction of a number of multiple service platforms (a platform is either hardware, software, or a combination of the two) in the marketplace. Many multi-service providers, e.g., telephone companies, are interested in this new generation of multi-service platforms because of their ability to support low cost, high performance Gigabit Ethernet and 10 Gigabyte Ethernet technologies. Ethernet based technologies offer a number of advantages, such as low cost, flexible architecture, flexible bandwidth, and a greater number of data services when compared to traditional TDM-based technologies such as SONET/SDH. Additionally, multi-service platforms allow the use of simpler, less expensive access equipment at a customer's site, e.g., inexpensive Layer-2 Ethernet devices and Layer-2-Layer-3 combination devices. Another advantage to Ethernet-based technologies is that the technology is widely known and deployed in local area networks. This results in lower cost and a wide selection of vendors. These platforms can forward packets based on both Layer 3 header information, e.g., IP, and Layer 2 header information (Ethernet MAC address, MPLS labels, etc.), and have enhanced traffic management capabilities. Based on these capabilities, packets may have different grades of quality of service (QoS) associated with them.
The simplest service to provide is a point-to-point connection between two subscriber interfaces. Packets from one interface are forwarded to another without modification (and vice versa). MPLS is considered to be the best technology to carry out point-to-point connections. In MPLS, a label is attached to each packet. The packet is then routed through the network to a terminal interface based on this label. The path that the packet takes is referred to as the “Label Switched Path” (LSP). As the packet travels through the network, the value of its label can be modified by each multi-purpose node it passes through. An LSP can be established using a “Label Distribution Protocol” (LDP). Two commonly used LDPs are “Resource Reservation Protocol with Traffic Engineering Extension” (RSVP-TE) and “Constraint Based” LDP (CR-LDP).
As MPLS packets are routed, network nodes may treat them differently depending on the value of certain bits within the label. For example, some packets may contain bits that identify them as high priority. The capability to track packets differently allows service providers to offer different QoS grades to their customers. To simplify the transmission of packets through a network, multiple LSPs between two MPLS nodes can be aggregated into a single, larger LSP by adding another MPLS label in front of the packet. This aggregation of LSPs offers several advantages. First, a “transit” node only needs to look at the exterior label because the exterior label contains information on the address of a “recipient” node. Second, network resources can be assigned to the aggregate LSP instead of the individual LSPs, which simplifies the management of the network. Aggregation of LSPs allows LSPs to share network resources, which is known as “statistical multiplexing.”
One Layer-2 service is “transparent” LAN service (TLS). TLS allows a network to appear as a segment of a larger LAN. A service provider provides TLS to its customer networks, where each customer network (e.g., a campus-like network) is logically separated from each other. Campus-like networks are commonly configured as Layer-2 virtual private networks (VPNs). The service they provide is referred to as a Layer-2 VPN service. An advantage of Layer-2 VPN service, compared to Layer-3 VPN service, is that it simplifies Layer-3 address administration (the dominant Layer 3 is Internet Protocol (IP)). The entire VPN can operate as a single Layer-3 subnet. Such Layer-2 service can support multiple Layer-3 protocols (more than just IP). With the introduction of new computer platforms and the abundant availability of high-speed connectivity, service providers are attempting to extend TLS service to networks other than campus-like networks, for example, to metropolitan-like networks.
The traditional method of implementing TLS is by using a number of bridging modules (BM) to form a network. To ensure reliability, each segment of a LAN is connected to multiple BMs. Similarly, each BM can be connected through multiple LAN connections. In order to avoid loops, only certain connections are “active.” The topographical configuration of a network showing its active connections is commonly referred as a “spanning tree” (e.g., such as that which is specified in the IEEE 802.1d standard). The IEEE 802.1d standard uses a protocol, know as the Bridge Protocol (BP), between BMs to determine the spanning tree of a network. Messages transferred using the BP are referred to as “bridge protocol data unit” (BPDU) messages.
In a traditional Layer-2 bridging network, the BMs are connected to one another through dedicated connections. Although they form a network, the BMs usually are not physically connected with each other. A spanning tree program ensures that all BMs are connected in an optimal manner. For instance, if all nodes are MPLS enabled, then all BMs can be directly connected through LSP tunnels.
It is desirable to develop improved techniques for ensuring that BMs are optimally connected. One suggested method is to directly connect all the BMs to one another through MPLS LSPs, alleviating the need of a spanning tree. However, this solution does not scale well. The network resources assigned to support each connection and the associated network costs are unacceptable because they exceed revenue. For example, a Layer-2 VPN with 4 nodes requires 6 bi-directional connections, and a Layer-2 VPN with 8 nodes requires 28 bi-directional connections. In general, a network with N nodes would require N*(N−1)/2 bidirectional connections (i.e., the number of connections grows at a rate proportional to the square of the number of nodes, N.)
Therefore, there is a need for techniques which make the use of MPLS LSPs more practical. In particular, there is a need for techniques that are capable of managing MPLS LSP connections within a VPN in order to reduce network costs, allow for better network management, and provide improved network throughput.